Gillian Duffy had only popped out to buy a loaf of bread. But by the time she
got home, following a chance encounter with the Prime Minister, the
65-year-old widow had become the woman who could seal the outcome of the
general election.

During an extraordinary address to a live television audience from the grandmother’s driveway he described himself as “a penitent sinner”.

Later, the premier emailed all Labour supporters — including candidates — to make clear his “profound regret” at what he had done.

Coming on the eve of today’s final televised leaders’ debate, some Cabinet ministers privately feared that the blunder had fatally undermined Labour’s campaign.

There was more bad news for Labour when it emerged that Mrs Duffy had been signed up by the PR firm Bell Pottinger, part of a group chaired by Lord Bell, Margaret Thatcher’s favourite PR man. She was thought to have signed an exclusive deal with a tabloid newspaper.

Mr Brown insisted that he was “mortified” by his outburst, claiming he had “misunderstood” what the pensioner had said to him. Mrs Duffy’s family suggested the public had been given an insight into the hypocrisy of the Prime Minister, who had laughed and joked with her in public before insulting her in private when he thought he was no longer being recorded.

Prime Ministerial aides also feared that millions of voters who shared Mrs Duffy’s measured views on immigration, policing, education and the economy would feel slighted by Mr Brown’s remarks.

Lance Price, a former Downing Street adviser under Tony Blair, said: “To sustain its share of the vote and maximise the number of MPs it returns, Labour needs the votes of millions of traditional supporters like Mrs Duffy.

“The party has lost not just hers, but potentially thousands of others who will listen to what she said and find that they agree. Does Brown think they are all bigots too?”

The Prime Minister had been visiting a community re-offender project in Rochdale when Mrs Duffy called out to him and asked why he was not addressing the debt crisis.

As part of the new “real voters” strategy, she was ushered by an aide to speak directly to the Prime Minister.

Mrs Duffy politely asked about a range of issues including the national debt, education and immigration.

She said: “You can’t say anything about immigrants... all these eastern Europeans are coming in, where are they flocking from?”

Mr Brown answered her questions and, as they parted, Mrs Duffy praised Labour education policy, describing Mr Brown as a “nice man” and telling reporters she had already filled in her postal ballot, voting Labour. As he got into his ministerial Jaguar, the Prime Minister complimented the former council worker for coming from “a good family” and said: “It’s very nice to see you. Take care.”

The discussion was destined to get little coverage on the day’s election broadcasts.

But Mr Brown was still wearing a microphone provided by Sky News, which recorded him turning to his aide Justin Forsyth, and pronouncing: “That was a disaster.”

He added: “Whose idea was that?” He then blamed “Sue” – Sue Nye his longest serving aide and friend.

He was then asked by the aide what Mrs Duffy had said.

He replied: “Everything, she was just a sort of bigoted woman who said she used to be Labour.”

The comments were relayed to Mrs Duffy who was aghast that Mr Brown – “a man who is going to lead this country . . . an educated person” – would make such an accusation.

She said: “I’m very upset. What was bigoted in what I said?” Mrs Duffy later said she would “rip up” her postal vote.

Minutes later, Mr Brown arrived for a BBC radio interview with Jeremy Vine. While he was live on air, Vine played the Prime Minister his comments. Seemingly unaware that he was being filmed, he held his head in his hand as he listened. His apology was stuttering and couched in equivocal language.

He said: “Of course I apologise if I have said anything that has been offensive and I would never put myself in a position where I would want to say anything like that about a woman I met.

“It was a question about immigration that I think was annoying.”

With the row dominating the afternoon, the Prime Minister was forced to abandon plans to prepare for tonight’s debate. He telephoned Mrs Duffy to say sorry and then went to her house to make another apology.

He said: “I am mortified by what has happened. I have given her my sincere apologies.”

Last night, the latest opinion polls showed the Tories extending their lead. A ComRes survey for The Independent put them on 36 per cent, Labour on 29 and the Lib Dems on 26. A YouGov survey for The Sun put the Tories on 34, the Lib Dems on 31 and Labour on 27 and a Harris poll for Metro put the Conservatives on 32 per cent, the Lib Dems on 30 and Labour on 25.